This thesis examines the role of the Northern Department of the British Foreign Office and its perception of, and attitude towards, the Soviet Union between 1945 and 1953. In these formative years after World War II many assumptions and policies were shaped that proved decisive for years to come. The Northern Department of the Foreign Office was at the centre of British dealings with the Soviet Union after 1945 in an atmosphere of cooling diplomatic relations between both camps. Keeping channels of communications open in order to exploit every opportunity for negotiation and the settlement of post-war issues, officials built up an extensive expertise of Soviet domestic and foreign policy. Their focus on all aspects of Soviet life accessible to them, for example, Soviet domestic and international propaganda, revealed in their view a significant emerging future threat to British interests in Europe and worldwide. This view provided the basis of the analysis of new information and the assessment of the best possible policy options for the British government. The Northern Department tried to exploit those traits of Soviet policy that could persuade the USA and Western Europe to follow British foreign policy initiatives vis-à-vis the Soviet Union in the early Cold War while attempting to balance those weaknesses that could harm this effort. The focus of the Department often varied as a result of Soviet action. Some issues, like the Cominform were of momentary importance while other issues, like the Communist threat and the issue of Western European defence remained on the agenda for many years. A realistic approach to foreign policy allowed officials to exploit and counter-act those Soviet foreign policies seen as most threatening to Britain and those most likely to aid Britain’s recovery of her much desired world role. While the initial optimism after 1945 soon faded and consolidation on both sides was followed by confrontation, officials in London and the embassy in Moscow tried to maintain diplomatic relations to aid Western recovery efforts and support the new foreign policy doctrine of containment. When by the early 1950s entrenchment was speeding up in East and West, the Northern Department nevertheless utilised the available information to support British foreign policy worldwide as well as strengthen the domestic effort to explain the increasing international tension to the British people. Realism on the part of officials, and awareness of the information and options available to them meant that a Britain closely allied to the USA but one that continued to talk to the Kremlin was seen as the best way to achieve a continued world role for Britain and a safe Europe.